Production of motor fuel



F. E. FREY Feb.`l2, 1946. i

PRODUCTIN oF MOTOR 'FUEL Filed. Feb. 27, 1942 INVENTOR FREDERICK E. FREYMMMQW I ATTORNEY HOLVNOILQVHd .M mZEml-O,

Paiement. 'laz 1946 l l escasos PRODUCTION or Moron FUEL I vFrisdrank E.Frey, Baruesviue, okia., assigner to f Phillips Petroleum Company, acorporation of Delaware ,Application February 27, 1942, sei-iai No.432,679v

(ci. 19e-1o) This invention relates to the conversion of hy.-drocarbohs. More particularly, it relates to the production of motorfuel from realtively lowboiling hydrocarbons by a process in whichhydrouoric acid is used as a catalyst. This application is acontinuation in part of my copending as distillation, to recover thefree hydrogen iluoride, and/or thermal decomposition and distillation,to recover the organically combined fluorine as hydrogen fluoride. v

I h'ave now found that spentor partly deactivated hydrofluoric acid fromthe alkylating step application, Serial No.7 315,063, flled January 22,

1940` (Patent No. 2,322,300?, and Serial No. 426,- 627, led January 13,1942. x

An object of this invention is to convert relatively low-boiling normalparaffinv hydrocarbons,

suchas normal butane and normal pentane, to higher-boilingsaturatedhydrocarbons.

A specic obj'ect of this invention is to produce j a motor fuel stockfrom relatively low-boiling paraiiins by a process in which usedhydrouoric aoidcatalyst from an alkylation step is used as a catalystfor isomerizingv normal parailin's to the isoparatlins required for thealkylation step.

Other objects and advantages of this invention will be apparent from theaccompanying description and discussion.

In the prior art of hydrocarbon conversion, it has been shown thatisoparamnsof relatively low molecular weight, such as isobutaneand/orisopentane4 can. be reacted in the presence ofl concentratedhydrofiuoric acid at a lcomparatively low temperature, for example, inthe range of Y Ofto 200 F., with alkylating reactants, such as olefinshaving 3 to 5 carbon atoms per molecule and corresponding alkylcompounds such as alkyl' halides, alcohols, esters, ethers, and thelike, preferably those of ,secondary or tertiary structure. to producemotor-fuel hydrocarbons thatjhave high antiknock values and that aresuitable for 'use in aviation gasoline. Normal paramns, such as normalbutane .and/or normal pentane, can also be alkylated, but only underconsiderably more drastic conditions, so that the product Iobtained byalkylating normal paramns is of lower quality in respect to octanenumber, and is produced in lower yield than that obtained by allavlatingthe corresponding isqparailins.

In such' alkylation processes. the hydrouoric acid'eventually becomes sospent or deactivated by acid-soluble organic and nuoro-organic materialthat it is 'unsuitedfor continued use: the

1 Spending or deactivation is especially rapid at elevatedtemperatureafsuch as those'required for the alkylatlon ofnormal'paramns. Disposal of the spent. acid is a considerable problem, becausecan -be advantageously used as an isomerizing catalyst to convertrelatively low-boiling normal parains, such as normal butane and/ornormal pentane, into isoparamns, such as isobutane and/ orisopentane. Ihave also found that the emuent from such a conversion can be used asfeed to han alkylation step, wherein theisoparafllns are converted tohigher-boiling motor-fuel hydrocarbons. Furthermore, I have found thatthe acid from the isomerizing conversion can .be puried in a relativelysimple manner so that it can be re-used in the alkylation step.

An understanding of' some aspects of my in- Yvention may be aided by theaccompanying drawing, which is a schematic flow-diagram. of onearrangement of equipment for practicing theinvention.

In the alkylating step of this invention, alsuitable hydrocarbonmaterial, for example` a mixture of normal butane and isobutane,isadmittedto alkylator Il, as through inlet II, valve I2, and pump I 3and/or through conduit 'I0 and pump 20. In alkylator Il, it is mixedunder alkylating conditions with an alkylating reactant, which 'may beadmitted throughinlet I5, valve I6, and

pump I1, and with concentrated hydrofiuoric acid, preferably anhydrous,which may be admitted through inlet Il, valve I9, and pump 20 and/orthrough conduit 10 and pump 20.

In the feeds to this alkylating step the weight ratio of isoparamns toolefins, or other alkylating reactant, preferably is in the range of 2:1to 20:1

i troduced into the reaction mixture under condi- I tions of highturbulence and/or in multipointwise v 'fashion, so that it is rapidlymixedwith the isoo1' the corrosive nature of the acid; lfurth'rmore,

heretofore no use for thejs'pent acid has been g known. Therefore, incommercial alkylation, it

. is necessary to provide acidfrecovery steps, such or more,` and theweight ratio of hydroiiuoric acid to total hydrocarbons preferably is inthe range 0.2:1 to 4:1, Th'e olefin preferably is inparamn reactant.This procedfure is advantaseous inorder to favor lthe desiredolefin-isoparamn ljunctures, or alkylation reactions. and to hinderundesirable olefin-olefin junctures, or D013?- f merization' reactions.Suitable operating'conditions'l in alkylator Il are a ,tenrrperaturev inthe v range -of 30 to 150". F., apressure sufncient to .maintain'allcomponents in the liquid phase, and

. a time of about Ito 30 or more minutes.

` .'I'n'e resulting mixture passes through conduit 2i A"and vvalvellltoseparator 2l, wherein it is '38 for use as catalyst in anisomerization-step to be described.

The lighter or hydrocarbon phase from separator 23 is passed throughvalve 24 and conduit 25 to fractionating means 26, in which it isseparated into the following six fractions: (1) a relatively minorfraction of relatively inert and difflcultly condensable gases, which isremoved through outlet 21 having valve 28; (2) a fraction comprisingpropane and hydrogen iiuoride, which is passed through conduit 29 andvalve 30 to separator 3l; (3) one or more fractions comprisingisoparafins, such as isobutane and/or isopentane, and at times also somehydrouoric acid,

which are recycled to pump I3, as through valve 32 and conduit 33; (4)'one or more fractions comprising normal pa'raiiins,y such as normalbutane and/or normal pentane, which are passed to pump 36, as throughvalve 34 and conduit 35; (5) a fraction of highly branched parafnicreaction products boiling within the motor-fuel range, which iswithdrawn through outlet 431 having valve 38, and (6) a relativelyhigh-boiling hydrocarbon residue, which is withdrawn through outlet 39having valve 40. Fractionating means comprises whatever distillingcolumns and auxiliary equipment are necessary or convenient foreffecting the separations indicated, as will be readily appreciated bythose skilled in the art.

In separator 3l the fraction comprising propane and hydrouoric acid isseparated into two phases as by cooling and gravitational or centrifugalmeans. The lighter or propane phase may be withdrawn through outlet 44having valve d5; the heavier or hydrouoric acid phase is passed throughvalve 46 and conduit 35 to pump 30. If desired, separator 3| may beby-passed, the hydrogen uoride and the propane then passing 'glroughvalve 4l and conduit 35 directly to pump In the isomerizing step of thisinvention, the materials from the alkylating step that come to pump 36through conduit 35, that is, a mixture of normal paraflins, such aspropane, butane, and

. normal pentane, with used or spent hydrofiuoric acid, is forced bypump 36 through heating coil 48, valve 49, and conduit 50 to reactor 5l.

In the feed to reactor 5i, the ratio of hydrouorio acid to hydrocarbonis preferably in the range from about 0.2:1 to 4:1 or more by weight;usually, operating with an acid-to-hydrocarbon ratio within this rangewill effect the maximum conversion of normal paraffins to isoparamns.-

These proportions are obtained by controlling the relative proportionsof spent acid from separator 23 which pass through valves 4 I and 43,respectively. Also, if desired, additional normal 'paraffl'n and/orhydrotluoric acid may be admitted to the system, as through inlets 52and/or 53 and valves 54 and/or B5, respectively.

The reaction temperature in reactor 5I may be within the range of about250 to l000 I". A

ment and operating costs, to use a pressure` in the range of 250 to 1000pounds per square inch. The reactiontime may be within the range of fromabout 1 to about 300 minutes, depending the temperature, since the timere- Y chieiiy upon Y quired decreases with increase in temperature. Ifthe reaction time is very short, such as 1 `to 5 minutes the reactioncan be completed in coil 48 4or an extension thereof; whereupon reactor5I may -be icy-'passed or removed fromv the system.

Preferably, the reaction zone is packed with a y contact mass, such assteel turnings,. alumina,

or other material resistant to corrosion by hydroiiuoric acid andsuitable for aiding the reaction' and heat transfer.

The resultant mixture from reactor 5I may be passed through valve 56 andconduit 5l to partial condenser 58, wherein, by a suitable coolingmeans, relatively high-boiling material, such as hydrocarbons boilingabove about the pentane range, water, acid-soluble material, and thelike, are liquened. Suitable conditions in the partial condenser are atemperature in the range of 125 to 400 F. and a corresponding pressurein the range of 15 to 400 pounds per square inch. The optimum conditionsfor any particular case are readily determinable by trial and/or fromwellknown vapor-pressure relationships of the various constituents.Conditions outside the ranges given above may 'be used, if desired ornecessary.

The resulting mixed-phase mixture from partial oondenser `5l; is passedthrough conduit 59 and valve t0 to separator 6i, wherein it isseptemperature within the range 400 to 800 F. is

usually preferred; at low temperatures the rate of reaction is low, andat high temperatures some cracking and carbon formation occurs. Thepressure may be within the range of atmospheric to 5000 pounds persquare inch or more; usually, it is preferred, for reasons of economy inequiparated into a gas phase and a liquid phase, as by gravitational orcentrifugal means. The temperature and pressure conditions should be, asnearly as possible, the same as in partial condenser 58. The liquidphase, kwhich comprises mainly hydrocarbons andacid-soluble substancesboiling approximately in the hexane range and above, is withdrawnthrough outlet 62 havingV valve 03. k The gas phase is passed throughvalve @d and conduit 65 to condenser and separator 66.

in condenser and separator 00, the gas phase from separator 5| is cooledand liquefied. The resulting mixture of acid and hydrocarbon phases,which comprises the isoparaiiins produced in reactor i, is passedthrough valve 69 and conduit ill to pump 20 for use as feed in thealkylation vheavy impurities areremoved from the catalyst and from thesystem. The material passed through valve 69 and conduit l0 to thealkylation step therefore contains lsoparafins and also concentratedhydroiuoric acid in a purified state suitable for catalyzing` thesubsequent'alkylation reaction. In some instances it may be possible topass a portion, or all, of the isomerization ellluent directly to thealkylation step, as through conduit l and valve, 14, with valve 56partially or completely closed. Such a procedure may be followed whenthe impurities in the elliuent from the isomerization are small, ornegligible, in amount. At other times it may be desirable to subject theisomerization eilluent to more complete separay tion, obtaining therebyin various separate frac- Y step is passed equipment, not shown, aswill-be appreciated by v those skilled in the art. Any fraction-sorecovered may be used in other steps of the process, and may beintroduced thereto through one or more appropriate conduits.

It is contemplated that the hydrofluoric acid can be, and in manyinstances will be, the isomerization catalyst, and I have obtainedsatisfactory isomerization and disproportionation of aliphatichydrocarbons using `hydroiluoric acid as the sole catalyticy material.However, in the broadest concept of the present invention, it is to beunderstood that the isomerization may be carried out in the presence ofother material in addition to hydrofluoric acid. Such other materialsmay serve to enhance the catalytic activity of hydrofiuoric acid; suchas material which provide large surfaces, to promote the ractivity ofhydrofluoric l acid, or to cooperate with the hydroiiuoric acid,

members of thislatter group having, themselves,

independent isomerization catalyzing activity.

Included among these groups. for use together with hydrofluoric acid',are the oxides and halides of beryllium, sulfur, tungsten, magnesium,alumi num, zinc, titanium, thorium, iron, copper, tin,

' vanadium, antimony, arsenic, chromium, molybdenum, manganese, nickeland cobalt, their salts c of difiicultly volatilizable acids, eithersynthetic or natural. Of the naturally occurring materials, I preferthose of large surface such as various clays, bauxite, brucite, etc.Sometimes activatedcharcoal ,may also be used to advantage. Thesevarious materials, or various ones oi' the materials mentioned may beused in granular form, as a powder, or may be pelleted, as may be foundfound most eiective or desirable in any particular instance.

A few o'i the many aspects vc: my invention are illustrated by thefollowing example, which is illustrative but not necessarily limitativeof the invention.

In an arrangement similar to that illustrated in theA accompanyingdrawing, normal butane' is prises relatively large proportions of normalparafhns and only small proportions of isoparainns, it is preferablyintroduced to fractionating means 28, as through inlet 'ii having valve12, instead of directly to alkylator il; whereupon the isoparanins areseparated out and passed to alkylator i4, and the normal paraiiins arepassed to the isomerization step. In another modification, theparafiinic feed material, instead of being ad- 'mitted directly toalkylator i4, or to fractionating means. 28, is admitted through inlet52, valve M, and pump 38 to the isomerization step; this modification isparticularly advantageous when the feed material has mostly low-boilingnormal parailins but practically no loW-boiling isoparail'ins.Additional pumps, valves, conduits, coolers, fractionators, and otherequipment, such as are well-known in the art qi hydrocarbon conversion,may be used wherever theyare necessary or convenient. 'I'he scope oi' myinvention should 'not be unduly limited by the numerical valuesdiscussed herein.

I claim:

l. Inaprocess for alkylating an isoparamn in the presence ofhydroiluoric acid, the improvement which comprises mixing a normalparaiiin with usedv hydroiluoric acid from an alkylating step,subjecting the resulting mixture to isomer-V izing conditions in anisomerizingstep, and using atleast part of. the eiiiuent from theisomerizing charged to -the isomerization stage, as through inlet 52;normal butylenes and concentrated lilydrofiuoric acid are separatelycharged to the alkylation stage, as through inlets I5 and il, re-

spectively. All of the acid used in the alkylation step.

The alkylating conditions are approximately las follows: temperature,102 F.; pressure, 150

pounds per square inch; time, 5 minutes; isobutane-to olefin molal'ratio (in the incoming ma terlals to the alkylation reactor), 11.5;hydrocarbon-to-acid weight ratio, 1.0; and rapid mix- 11,18 to maintainintimate contact between the acid A and hydrocarbon phases.

'I'he isomerizing conditions are approximately' as follows: temperature,850 F.; pressure, 2,000 pounds per square inch; time,'10 to 80 minutes.From this process, there is produced in a yield of aboutv 160 per cent,based on the weight of olefins charged, an aviation motor fuel which hasa clear octane number of about 90.

In this process, the acid eiliuent from the alkyl ation step is used ascatalyst in the isomerization step; it is then purified by partialcondensation,

as in condenser 68, and is returned to the alkylation step.

My invention provides a process for utilizing normal parafllns,particularly low-boiling paramns such as normal butane and/or normalpentane, to produce relatively high-boiling saturated as catalyst to theisomerization step as ieed material in the alkylating step.

2. In the process of claim 1, cooling the eiiiuent from the isomerizingstep to remove by partial condensation material which boils above aboutthe pentane range prior to using said efiiuent as feed material in thealkylating step.

3. A process for producing motor fuel, which comprises: alkylating alow-boiling isoparaiiin of four to five carbon atoms per molecule withan olefin of three to 'five carbon atoms per molecule in the presence ofconcentrated hydrouoric acid in an alwlation step; separating theeffluent from -said alkylation step into a hydrofluoric acid iraction,at least one low-boiling isoparaiiin fraction, at least one low-boilingnormal paraiiin fraction, a motor-fuel fraction, and aheavier-than-motorfuel fraction; removing from the process saidmotor-fuel and heavier-thansmotor-:fuel fractions; recycling saidlow-boiling isoparamn 'fraction to the alkylation step; Passing saidhydroiluoric acid and low-boiling normal paraffin fractions to anisomerization step in which such conditions are maintained that normalparaflins are' isomerized to a substantial extent by hydro fluoric acidinto isoparaiiinm'freeing the resulting effluent-from the isomerizationstep from materialfboiling above about the pentane range by partialcondensation; and passing the thus freed eiiluent to said alkylationstep.

4. A process for producing normally liquid iso- I paramnic hydrocarbonsfrom lower boiling norhydrocarbons of high antiknock value that are malparadin hydrocarbons etat least i'ourv carbon ralkylatirig reactant invin the presence of concentrated hydrouoric acid to produce alow-boiling isoparailn hydrocarbon, reacting said isoparaffin soproduced with an the presence of concentrated hydrouoric acid as thealkylation catalyst to produce normally liquid isoparafns ofliighermolecular weight, separating from effluents of said alkylation ahydrocarbon traction containing liquidv isoparafns so produced as aproduct of the process, separating also from eiiluents of saidalkylation a hydrofluoric acid fraction, Yand passing said fraction tosaid isomerization.

5. A process for producing normally liquid isoparafiinic hydrocarbonsfrom lower boiling normal parafiln hydrocarbons of at least four carbonatoms per molecule, which comprises subjecting such a normal paraflin tocatalytic isomerization in the presence of concentrated hydrofluoricacid as the isomerization catalyst to produce a lowboiling isoparainhydrocarbon, reacting said iso-l paraiiin so produced with an alkylatingreactant in the presence of concentrated hydrofluoric acid as thealkylation/ catalyst to produce normally liquid isoparains of' highermolecular weight, separating from efuents of said alkylation ahydrocarbon fraction containing liquid isoparafns so produced as aproduct of the process, separating also from effluents of saidalkylation a hydrofiuoric acid fraction, and passing said fraction tosaid isomerization as the isomerization catalyst.

6. A process for producing normally liquid isoparalnic hydrocarbons froma mixture of low- .boiling isoparaflins and normal parains of at leastfour carbon atoms per molecule, which comprises separating anisoparailln fraction and 'a normal paraiiln fraction from said mixture,re acting said iso parafiln fraction in an alkylation step with analkylating reactant in the presence of concentrated hydrouoric acid asthe -alkyla= tion catalyst to produce higher-boiling isoparaf- `iins,separating from eiiluents of said alkylation higher-boiling isoparafnsvso produced as products of the process, separating also from effluentsof said alkylation an impure liquid hydroluoric acid, passingA saidliquid hydroluoric acid together with the aforesaid nonmal parafllnfraction to an lisomerization step to isomerize said normal paraiins,

parailins and form low-boiling isoparafns, and

recovering low-boiling isoparafilns so formed andv paraiilnichydrocarbons from lower boiling paraf- 1in hydrocarbons, which comprisessubjecting aV low-boiling normal paraiiln hydrocarbon of at least fourcarbon atoms per molecule to isomerization in the presence' ofhydrofiuoric acid as the isomerization catalyst at a temperature withinthe range of 250 to 1000" F. and a superatinospheri'c pressure toproduce low-boiling isosubjecting the effluent of said isomerization tocooling and partial condensation to condense material .boiling abovepentanes and removing material so condensed from the system, subjectinguncondensed material/to further cooling and condensation to condensehydrofluoric acid and low-boiling isoparaflins, separating rnaterial socondensed from uncondensed gases, passing. the last said condensedmaterial to an alkylation zone and reacting isoparafilns containedtherein with an added alkylating reactant .in the presence of saidhydrofluoric acid and as the allrylation catalyst to produce normallyliquid isoparains, separating from the effluent of said alkylation aliquid hydrofluoric acid phase, and passing said hydrofluoric acidphase-to said isomerization. Y

8. In a process for producing parafn hydrocarbons boiling in the motorfuel range from lower-boiling parafn hydrocarbons, the improvem mentwhich comprises subjecting a normal paraf lin an alkylation step with anfin of four to ve carbon atoms per molecule in an isomerization step tocatalytic isomerization in the presence of used hydrofluoric acidobtained from a subsequent alkylation step, separating from efiluents ofsaid isomerization a low-boiling isoparafiln' so produced, reacting saidisoparaiiin alkylation reactant in the presenceof concentratedhydrouoric acid as the alkylation batalyst to produce parafflns boilingin the motor fuel range, passing eiiluents of said alkylation to aseparator and effecting a separation between a hydrocarbon phase and ahydroiiuoric acid phase, and passing at least a portion of saidhydrofluoric acid phase to said isomerization step.

FREDERICK E. FREY.

